Abstract
Overall Antarctic sea ice extent in the 2016 spring attained a record minimum for the satellite period (1979–2016), presenting an abrupt departure from the record maxima in previous years and the slight upward trend since 1979. In 2016 the atmospheric conditions over the Southern Ocean changed dramatically from the prevailing cold and westerly anomalies in summer to warm and easterly anomalies in spring. We conducted numerical experiments with an ocean-sea ice model to quantify the major factors responsible for the unanticipated change in 2016. Our model successfully reproduces the long-term increasing trend and the 2016 minimum, and the numerical experiments suggest that the 2016 minimum event is largely attributable to thermodynamic surface forcing (53%), while wind stress and the sea-ice and oceanic conditions from the previous summer (January 2016) explain the remaining 34% and 13%, respectively. This confirms that it is essential to assess the thermal conditions in both the atmosphere and ocean when estimating Antarctic sea ice fields to future climate changes.
Highlights
Contrary to the dramatic decrease in Arctic sea ice coverage (Cavalieri and Parkinson 2012), overall sea ice extent (SIE)/area around Antarctica has modestly increased since 1979 (Parkinson and Cavalieri 2012, Comiso et al 2017, De Santis et al 2017)
The sea surface temperature (SST) anomalies in ‘INI + THD’ series, on the other hand, are similar to those in the ‘ALL’ case and the ‘THD + DYN’ ensemble mean, but with a smaller amplitude of anomalies. These results suggest that thermodynamic surface forcing associated with atmospheric circulation change is responsible for the broad observed regional negative sea ice concentration (SIC) anomalies in the 2016 sea ice edge, except for the western Weddell Sea and western Pacific Ocean sectors, and the broad SST anomaly fields around the entire Southern Ocean
We have investigated key factors responsible for the extraordinary 2016 Antarctic sea ice minimum, based on analyses of atmospheric re-analysis data and results from a coupled ocean-sea ice model
Summary
Kazuya Kusahara1,2 , Phillip Reid, Guy D Williams, Robert Massom and Hiroyasu Hasumi.
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